I went to buy a book. There were a chaos of options in the used list at the same price. Because these were used, there were descriptions of quality headlined with:

Acceptable

Good

Very Good

Like New

All but new were represented at the cheapest price level. So naturally I looked through the very goods for the best described one. It felt more involved because I had to glance at dozens to find the 3 VGs. And re-check to make sure I had found them.

Being raised in libraries, it seemed to me like this needed an order tweak. It seemed like in addition to the existing order of lowest to highest, it should also order best quality to worst. So the first result is the cheapest price with best quality.

Then the behavior economist in me realized that the used book dealers would exploit that model. They would have a stronger incentive to inflate the quality of their book. Suddenly former library books they list as Good would find their way to Like New quality. Everyone wants the first spot because people are lazy and much more likely to buy the one there. If a seller wants to undercut competition by using a lower price, then that race to the bottom reflects supply and demand. When there are lots of books, buyers benefit by picking the cheapest.

Quality is a different animal. It is the area where buyers have to beware. Only the seller really knows the true quality of the item. The buyer only finds out upon receiving it. That kind of imbalance is where the free hand of the market tends to be tied behind its back. Sure, the buyer can complain and contest, but that really means buyers stop trusting this specific place and go elsewhere.

Easier is to take away the incentive to falsify the quality of books by putting the order random at the same price level. So my guess is that is why it is that way.